From e857a27d5bca6269cea7a0ca0058aa8fffe90a83 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Fri, 25 Sep 2020 15:07:23 +0100
Subject: [PATCH] net: bcmgenet: Reset RBUF on first open

If the RBUF logic is not reset when the kernel starts then there
may be some data left over from any network boot loader. If the
64-byte packet headers are enabled then this can be fatal.

Extend bcmgenet_dma_disable to do perform the reset, but not when
called from bcmgenet_resume in order to preserve a wake packet.

N.B. This different handling of resume is just based on a hunch -
why else wouldn't one reset the RBUF as well as the TBUF? If this
isn't the case then it's easy to change the patch to make the RBUF
reset unconditional.

See: https://github.com/raspberrypi/linux/issues/3850

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 drivers/net/ethernet/broadcom/genet/bcmgenet.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -3306,7 +3306,7 @@ static void bcmgenet_get_hw_addr(struct
 }
 
 /* Returns a reusable dma control register value */
-static u32 bcmgenet_dma_disable(struct bcmgenet_priv *priv)
+static u32 bcmgenet_dma_disable(struct bcmgenet_priv *priv, bool flush_rx)
 {
 	unsigned int i;
 	u32 reg;
@@ -3331,6 +3331,14 @@ static u32 bcmgenet_dma_disable(struct b
 	udelay(10);
 	bcmgenet_umac_writel(priv, 0, UMAC_TX_FLUSH);
 
+	if (flush_rx) {
+	    reg = bcmgenet_rbuf_ctrl_get(priv);
+	    bcmgenet_rbuf_ctrl_set(priv, reg | BIT(0));
+	    udelay(10);
+	    bcmgenet_rbuf_ctrl_set(priv, reg);
+	    udelay(10);
+	}
+
 	return dma_ctrl;
 }
 
@@ -3394,8 +3402,8 @@ static int bcmgenet_open(struct net_devi
 
 	bcmgenet_set_hw_addr(priv, dev->dev_addr);
 
-	/* Disable RX/TX DMA and flush TX queues */
-	dma_ctrl = bcmgenet_dma_disable(priv);
+	/* Disable RX/TX DMA and flush TX and RX queues */
+	dma_ctrl = bcmgenet_dma_disable(priv, true);
 
 	/* Reinitialize TDMA and RDMA and SW housekeeping */
 	ret = bcmgenet_init_dma(priv);
@@ -4269,7 +4277,7 @@ static int bcmgenet_resume(struct device
 			bcmgenet_hfb_create_rxnfc_filter(priv, rule);
 
 	/* Disable RX/TX DMA and flush TX queues */
-	dma_ctrl = bcmgenet_dma_disable(priv);
+	dma_ctrl = bcmgenet_dma_disable(priv, false);
 
 	/* Reinitialize TDMA and RDMA and SW housekeeping */
 	ret = bcmgenet_init_dma(priv);
